使用负前瞻正则表达式的Java输入检查

Question

I am trying to using a regex negative lookahead to check if any invalid characters have been entered. The characters I want to check for are everything but 0-9, whitespace, *, /, +, -, r, x.

String word = "(l4+3q)*(5+7-8)/(5)";
Pattern p  = Pattern.compile("(?![\\d\\srx*+-/)]+)");
Matcher m = p.matcher(word);

if(m.matches()) System.out.println("NO");

In this current test code, every string I use returns false.

Could anyone provide me with some direction on how to modify this regular expression to work for my specifications.

Answer 1

You don't want to use this +-/ in that order in the class.
The - used this way is a range operator, not a literal -.
To make it literal, add it to the end or beginning, or escape it
and it can be anywhere.

Basically, you want to match anything not in that class.
Pattern p = Pattern.compile("[^\\\\d\\\\srx*+\\\\-/)]");

If it matches if( m.matches() ) it did find an illegal character.
or,
If it doesn't match if( !m.matches() ) it didn't find an illegal character.